Field of the Invention
The present invention relates to a vibration sensor with a bonded drive.
Background of the Invention
The prior art discloses vibration sensors that are used, for example, as vibration limit switches. In this case the vibration sensor has a membrane, which can be excited to vibrate by a drive and by means of which the mechanical oscillator, which is mounted on the membrane, can be excited to vibrate. Independently of the state, in which the mechanical oscillator is covered with a filling material and independently of the viscosity of this filling material, this mechanical oscillator vibrates at a characteristic frequency that can be detected by the vibration sensor and can be transformed into a measurement signal.
It is well-known to use a bonded drive in such vibration limit switches, wherein in order to produce an adhesive layer on the membrane, an adaptor ceramic element is bonded with the membrane, and on said adaptor ceramic element in turn an adhesive layer is applied, and with this adhesive layer a piezo actuator is bonded, and then finally contact is made with said piezo actuator by means of a flexible printed circuit board, a so-called flex circuit board. In the above described production process it is difficult to bond the individual components one on top of the other with uniformly thin adhesive layers, because the thickness of these adhesive layers varies as a function of the viscosity of the adhesive, the amount of adhesive that is used and the contact force that is applied. However, adhesive layers of different thickness have an impact on the targeted measurement results, and thus lead to undesired deviations of the measurement results.
Moreover, it has proved to be disadvantageous that in the above described assembly process, the individual components are held concentric to one another, and that said individual components have to be placed in such a way that they are centered relative to the membrane. To date the known prior art has achieved these requirements by using a housing made of a synthetic plastic material, in order to center the individual components and for the bonding process.
The object of the present invention is to make available an improved vibration sensor that avoids the drawbacks known from the prior art.
This engineering object is achieved by means of a vibration sensor and a method for producing a vibration sensor exhibiting the features disclosed herein.